using tropical cyclone wind speed probabilities to improve public and marine text forecasts

Pablo Santos and Guy RaderWFO Miami, FL

David Sharp and Matthew VolkmerWFO Melbourne, FL

From the 2007 NOAA Hurricane ConferencePS/DS

“HURRICANE CONDITIONS EXPECTED.”

Using Tropical CycloneUsing Tropical CycloneWind Speed Probabilities to ImproveWind Speed Probabilities to Improve

Public and Marine Text ForecastsPublic and Marine Text Forecasts

Module #1

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Two Training ModulesTwo Training Modules

• Module #1: Concepts for Using Tropical Cyclone

Wind Speed Probabilities to Generate

Expressions of Uncertainty

• Module #2: Applying Expressions of Uncertainty

to the ZFP and CWF during

Tropical Cyclone Wind Situations

In Support of an Experimental Project for 2008

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Training Module (1 of 2)Training Module (1 of 2)

• Module #1: Concepts– Motivation– Overview and Background– Probability Concepts– Situational Thresholds

• gridded inputs– Expressions of Uncertainty

• unique expressions• text formatters

– Future Plans

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ObjectivesObjectives

• To better understand the shortcomings of deterministic-only wind speed forecasts during high impact weather events.

• To gain a greater appreciation for the value of probabilistic wind speed information and how incremental probabilities can be used to improve certain text products.

• To become familiar with the nine identified expressions of uncertainty and the unique situations that invoke them.

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Wind Speed ProbabilitiesWind Speed Probabilities

Interval Probabilities & Cumulative Probabilities

Cumulative – 64 knot

PWS

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Probability DefinitionsProbability Definitions

• Cumulative – The probability of sustained winds reaching or exceeding the specified wind speed threshold between the 00 hour forecast and a specified forecast hour.

• Available in D2D and within the PWSAT# text product.

• Individual (Interval) – The probability of sustained winds reaching or exceeding the specified wind speed threshold beginning during an individual 12 hour forecast period ending at the specified forecast hour (e.g., period of onset).

• Not available in D2D, but within the PWSAT# text product.

Incremental –The probability of sustained winds reaching or exceeding the specified threshold during the 12 hour forecast period ending at the specified forecast hour.

• Now available in D2D (across the SBN), but not within the PWSAT#.

• These are the probabilities referenced throughout this presentation.

(A Quick Review)

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Incremental ProbabilitiesIncremental Probabilities

• Incremental –The probability of sustained winds reaching or exceeding the specified threshold during the 12 hour forecast period ending at the specified forecast hour.

• Now available in D2D (across the SBN), but not within the PWSAT#.

What do they look like?

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34 Knot (36 Hours)TC Wind Speed Probabilities on AWIPS-D2D(Incremental-form for 34-, 50-, and 64-knots)

34 knot / 36 hour

= EXAMPLE =

Hurricane Charley 2004

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34 Knot (48 Hours)

Hurricane Charley 200434 knot / 48 hour

= EXAMPLE =TC Wind Speed Probabilities on AWIPS-D2D(Incremental-form for 34-, 50-, and 64-knots)

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• During potential high impact weather events such as tropical cyclones (TC), users not only demand our ‘best forecast’, but also require a corresponding expression of uncertainty for decision-making purposes.

• Therefore, we are exploring the use of TC Wind Speed Probabilities to elevate the utility of official text products:– That is, to include situational expressions of

uncertainty within the Zone Forecast Product (ZFP) and the Coastal Waters Forecast (CWF).

– For WFOs, this effort crosses a major threshold for incorporating probabilistic data (other than PoP) within official National Weather Service forecast products.

Proposed WFO UseProposed WFO Use (Item 42-05 from NOAA Hurricane Conference, 2005)

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FRANCES (ZFP)FRANCES (ZFP)

Point-n-Click Web VersionPoint-n-Click Web Version

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Rules for FormattersRules for Formatters

• The intent is to establish a set of rules for triggering enhanced wording which responsibly conveys wind speed uncertainties within text forecasts according to the temporal period.

• This is accomplished through the Graphical Forecast Editor (GFE) and automated formatters by making appropriate use of the following grids sets:– Hazard Grids– Wind Grids– Tropical Cyclone 34 kt Wind Speed Probability Grids – Tropical Cyclone 64 kt Wind Speed Probability Grids

• Initial development and testing was done during the 2005-06 seasons by WFOs MFL and MLB. The experimental effort was then expanded during the 2007 season to include a few more WFOs, with HGX playing a critical role. The good news is that more WFOs are being included for the 2008 season, with the Point-n-Click functionality also making its debut.

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Grid Set DescriptionsGrid Set Descriptions

• The Hazard Grids include Hurricane/Tropical Storm Warning/Watch grids as issued:– For coastal zones by NHC– For inland zones by WFO– For marine zones by WFO

• The Wind Grids represent the sustained wind speed forecast as generated by the TCM Wind tool (from the latest NHC forecast), but with WFO value-added contributions for local effects (e.g., elevation, exposure, gap winds, etc.).

• Again, the Tropical Cyclone Wind Probability Grids (as obtained through TPC) are the incremental-form probabilities for 34 knot and 64 knot winds.

• The incremental probabilities for 50 knot winds are not needed for this application.

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Text Formatters: Logic Hierarchy Priority Sensitivity Grid Sets

1. Official Warnings,

Official Watches

Hazard Grids

2. Official Forecast Wind Grids (Speed)

3. Forecast Uncertainty 64-knot Probability Grids,

34-knot Probability Grids

Note: Forecast Uncertainty implies appreciation for the inherent errors regarding the forecast track, intensity, and size of the tropical cyclone.

Message SensitivityMessage Sensitivity(Fostering One Forecast Message)

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(The Nine Expressions of Uncertainty) • HURRICANE CONDITIONS *• HURRICANE CONDITIONS EXPECTED• HURRICANE CONDITIONS POSSIBLE

• TROPICAL STORM CONDITIONS *• TROPICAL STORM CONDITIONS * WITH HURRICANE CONDITIONS POSSIBLE• TROPICAL STORM CONDITIONS EXPECTED• TROPICAL STORM CONDITIONS EXPECTED WITH HURRICANE CONDITIONS POSSIBLE• TROPICAL STORM CONDITIONS POSSIBLE• TROPICAL STORM CONDITIONS POSSIBLE WITH HURRICANE CONDITIONS ALSO POSSIBLE

• The * phrases are equivalent to imminent or ongoing conditions as reflected in the 00-12 hour period simultaneously by the hazard, wind, and probability grids. • The word EXPECTED is used in situations mainly during the Warning period, but is also selectively used in the Watch period (e.g., Day 1 & 2, or out to period 4).• The word POSSIBLE is used during the extended period (e.g., Day 3 - 5), but is also used in specific situations within Watch/Warning period. • Also, certain situations require compound phrases (e.g., when there is a Tropical Storm Warning with a Hurricane Watch).

Baseline PhraseologyBaseline Phraseology

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(First Period: When conditions are IMMINENT or ONGOING)

For a given zone or zone combination, in order to consider a situation as being imminent or ongoing within the first period of the text forecast requires:

• Tropical Storm (Hurricane) Warnings to be in effect…AND…maximum Wind forecast to be greater than or equal to 34 knots (64 knots)...AND…the 34 knot (64 knot) Probability to be greater than or equal to the PWS34 threshold (PWS64 threshold).

Phrase Period PWS64 PWS34

‘Imminent’ or ‘Ongoing’

00-12 hr 30% 70%

Note: Initial probability thresholds were empirically-determined; future refinementsare likely. This is true for each temporal interval of the forecast.

TriggersTriggers

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For a given zone or zone combination, invoking the word EXPECTED for the specified period of the text forecast requires: • Tropical Storm (Hurricane) Warnings to be in effect…AND…maximum Wind forecast to be greater than or equal to 34 knots (64 knots)…OR…

• Tropical Storm (Hurricane) Warnings to be in effect…AND…maximum Wind forecast to be greater than or equal to 25 knots (50 knots)…AND…the 34 knot (64 knot) Probability to be greater than or equal to the PWS34 threshold (PWS64 threshold) according to the forecast period.


EXPECTED 00-12 hr 15% 50%

13-24 hr 12% 40%

25-36 hr 10% 35%

37-48 hr 9% 30%

(Periods 1-4: When conditions are EXPECTED)

TriggersTriggers

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POSSIBLE 00-12 hr 15% 50%

13-24 hr 12% 40%

25-36 hr 10% 35%

37-48 hr 9% 30%

49-60 hr 8% 25%

61-72 hr 7% 20%

73-84 hr 6% 17.5%

85-96 hr 5% 15%

97-108 hr 4% 12.5%

109-120 hr 3% 10%

According to the situation, the word POSSIBLE can be invoked anytime throughout the five-day forecast, and is the qualifier most often used within the enhanced phrasing. Within the 00-48 hour forecast, if imminent/ongoing criteria are not met, or EXPECTED criteria are not met, the word POSSIBLE is used whenever the probability thresholds are exceeded for the given time period. In the extended (e.g., beyond 48 hours), an additional constraint of winds > 20 knots is imposed.

(Periods 1-10: When conditions are POSSIBLE)TriggersTriggers

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For a given zone or zone combination, invoking the word POSSIBLE for the specified period of the text forecast requires:

• From the Hazard Grids Perspective…a Tropical Storm (Hurricane) Warning to be in effect with maximum Wind and/or Probability criteria met, but criteria for imminent/ongoing conditions or EXPECTED conditions not be met…OR…

• Also From the Hazard Grids Perspective…a Tropical Storm (Hurricane) Watch to be in effect with maximum Wind or Probability criteria met…OR…

• From the Wind Grids Perspective…the maximum Wind to be greater than or equal to 25 knots when there is also a Watch/Warning in effect…OR…

• Also From the Wind Grids Perspective…the maximum Wind forecast to be greater than or equal to 34 knots (64 knots), but Watches/Warnings not be in effect…OR…

• From the Probability Grids Perspective…the 34 knot (64 knot) Probability to be greater than or equal to the PWS34 threshold (PWS64 threshold) according to the forecast period, regardless of whether there are Watches/Warnings in effect. In the extended periods, in addition to the probability threshold criteria, the forecast wind must also be 20 knots or greater.

TriggersTriggers(Periods 1-10: When conditions are POSSIBLE)

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Hurricane Wilma (2005)Hurricane Wilma (2005)Hazard Grids Input

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Algorithm ExampleAlgorithm Example

WILMA (CWF)WILMA (CWF)

Contoured Wind Speeds 0-24 knots 25-33 knots34-49 knots 50-63 knots 64+ knots

Wind Grids Input

Advisory Time: 20051023_2100 (First through Third Periods)

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Hurricane Wilma (CWF)


Advisory Time: 20051023_2100 (First through Third Periods)Algorithm ExampleAlgorithm Example

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Hurricane Charley - UpdateHurricane Charley - Update

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Hurricane Charley (ZFP)

Advisory Time: 20040813_1500 (0-12 Hours – First Period)

Morning Update

CHARLEY (ZFP)CHARLEY (ZFP)

* Naples

A Second Algorithm ExampleA Second Algorithm Example

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Morning Update


* Naples

A Second Algorithm ExampleA Second Algorithm ExampleAdvisory Time: 20040813_1500 (0-12 Hours – First Period)

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* Punta Gorda

Advisory Time: 20040813_1500 (0-12 Hours – First Period)A Second Algorithm ExampleA Second Algorithm Example

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• Conduct experiment during 2008 season– Generate case study examples from other locations and with an

increasing variety of storms (real-time or archived)– Validate probability thresholds; perform ROC Diagram study– Evaluate consistency issues between the ZFP/CWF and their web

page Point-n-Click counterparts– Evaluate consistency issues advisory to advisory– Compile experiences and share with the Tropical Cyclone Wind

Team (present to NOAA Hurricane Conference - 2008)

• Iterative Decision Points (considering user benefits) – Continue experimentally, implement officially, or discontinue– ZFP and CWF products – Click Point forecast web pages– Consider other applications (e.g., Point Forecast Matrices, etc.)

Current & Future WorkCurrent & Future Work

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SummarySummary

• This completes Module #1

• Please review Module #2 – Applying Expressions of Uncertainty to the

ZFP and CWF during Tropical Cyclone Wind Situations

Thank You !!!

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Tropical Cyclone Impacts GraphicsTropical Cyclone Impacts Graphics

Threat Assessment

David Sharp, Pablo Santos, Tom LeFebvre, Frank Alsheimer, and Tim Schott

Potential Impact

DS/PS 2008

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Hazard >> Threat >> ImpactHazard >> Threat >> Impact

• TC Hazards include high wind, storm surge and tide, flooding rain, and tornadoes.

• Coastal WFOs (participating in the experiment) execute TC Threat Assessment Tools once tropical cyclone watches or warnings are issued for their forecast area. These tools consider:– forecast magnitude of hazard– forecast uncertainty of hazard

• Final output is in the form of TC Potential Impact Graphics which are posted to the web as an experimental service.

• Depictions are valid for the duration of the event, locally, but updated with each successive advisory from NHC, to include updates from HPC and SPC.

Inland Flooding Impact

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Potential Impact GraphicsPotential Impact Graphics

• The associated hazard is identified.– In context of event

• The corresponding threat is quickly assessed through software applications and then delivered to the forecaster for limited editing. These SmartTools provide:

– Automated first-guess fields on GFE– WFO forecaster expertise optionally applied– Output is converted to *.png graphics

• The result is a simplified graphical expression that has been interpreted in terms of potential impact and provided to users via the web.

– Color-coded graphics (and eventually grids)– Customer language– Locally calibrated definitions

From the Practical Perspective:


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National Web SiteNational Web Site(Participating Coastal WFOs – 2008)

http://www.weather.gov/os/tropical/index.php

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Graphics & DefinitionsGraphics & Definitions

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This is This is “Cool Stuff”“Cool Stuff” !!! !!!

http://lucretia.srh.noaa.gov/coolstuff/tropical_graphics/index.php

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The High Wind HazardThe High Wind Hazard

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High Wind - Tool InputsHigh Wind - Tool Inputs

Threat Assessment

64 KTS Cumulative Probabilities

Deterministic & Probabilistic Gridded Input

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Deterministic WindDeterministic Wind

Jeanne (04)

WFO Wind Grids• NHC Official Forecast• WFO Enhancements

• Mesoscale interactions• Terrain altitude• Windward vs. Leeward

• islands• mountains

• Gap winds• Large inland lakes• And so on…

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Logic Summary - High WindLogic Summary - High Wind

Potential Impact Gridded Threat Assessment (for Peninsular Florida)

Very Low> 10% chance of 34 kt and <10% chance of 50 kt

…OR… 34 to 49 kt gridpoint winds

Low> 10% chance of 50 kt and < 10 % chance 64 kt

…OR…50 to 63 kt gridpoint winds

Moderate> 10% chance of 64 kt and 84 kt (Cat 2 by TPC) is not forecast …OR…64 to 83 kt gridpoint winds

High> 15% chance of 64 kt if 84 kt (Cat 2 by TPC) is forecast and > 96 kt (Cat 3+ by TPC) is not forecast …OR…84 to 95 kt gridpoint winds

Extreme> 25% chance of 64 kt if > 96 kt (Cat 3+ by TPC) is forecast …OR… > 96 kt gridpoint winds

Note: To invoke the logic for the High and Extreme levels requires forecast winds of 84 knots (Cat 2) and 96 knots (Cat 3+) anywhere within the GFE domain.

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High Wind – Tool InterfaceHigh Wind – Tool Interface

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High Wind – Tool InterfaceHigh Wind – Tool Interface

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Potential Impact GraphicPotential Impact Graphic

High Wind Impact

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Run-to-Run BehaviorRun-to-Run Behavior

• Potential Impact Graphic (left) and NHC forecast (right) for Hurricane Charley 30 hours prior to landfall.

• Storm strengthened rapidly just prior to landfall and made landfall at Punta Gorda.

• The impact graphic shows that Tampa and Punta Gorda were both subject to an extreme impact. Both cities should have been preparing for a major hurricane!

A

B

Tampa Bay (A) vs. Punta Gorda (B)Hurricane Charley (04)

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Inland Wind ImpactsInland Wind Impacts

Hurricane Charley – 081304_18z_highwind

Initial Output From TCWindThreat Tool

From NOAA/HRD

Orlando

Arcadia

Punta Gorda

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Consistency & ContinuityConsistency & Continuity

Wilma Wind Threat 10/22/05 21z

Just over 36 hours from landfall on the SW Florida coast

Minor tweaks by forecaster to handle slightly higher winds along the coast from KSC south.

Matches up WFO to WFO as with other GFE elements.

Potential Impact - Wind Potential Impact - Wind

MLB MFLInitial output from tool.

Hurricane Wilma (05)

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The Surge and Tide HazardThe Surge and Tide Hazard

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Coastal Flooding - Tool InputsCoastal Flooding - Tool Inputs

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Approach: Utilize gridded probabilistic and deterministic storm surge input for the Surge Threat tool much like the Wind Threat tool.

10% Exceedance

Deterministic (SLOSH composite max) Probabilistic (as developed by MDL)

Wilma (05)

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Logic Summary – Surge + TideLogic Summary – Surge + Tide

Potential Impact Gridded Threat Assessment (for Peninsular Florida)

Very Low10% chance of > 1 ft, but < 2 ft

…OR…1.0 to 1.9 ft gridpoint surge (and tide)

Low10% chance of > 2 ft, but < 4 ft

…OR…2.0 to 3.9 ft gridpoint surge (and tide)

Moderate10% chance of > 4 ft, but < 6 ft …OR…4.0 to 5.9 ft gridpoint surge (and tide)

High10% chance of > 6 ft, but < 8 ft …OR…6.0 to 7.9 ft gridpoint surge (and tide)

Extreme10% chance of > 8 ft …OR…8.0+ ft gridpoint surge (and tide)

Note: Due to the degradation in resolution when performing the assessment in GFE, the resulting impact graphic is not meant to function in the same way as an inundation map.

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The Surge+Tide ToolThe Surge+Tide Tool

• Threshold heights are established according to area concerns.

• The GUI is set to default at traditional threshold heights, but can be manipulated through slider bars if desired.

• The slider bar values must match your select threshold heights which correspond to your impact definitions on the Web site.

• Also, you can simply add-on the effects of tide on top of your surge. However, more tool work is need to improve the effects of tide.

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The Surge+Tide ToolThe Surge+Tide Tool

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The Flooding Rain HazardThe Flooding Rain Hazard

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Inland Flooding - Tool InputInland Flooding - Tool Input

RFC Gridded FlashFlood Guidance (6 hr)

WFO QPF (6 hr)

ERP Grid

QPF/FFG Ratio

HPC


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Logic Summary - Inland FloodingLogic Summary - Inland Flooding

ERP QPF/FFG Ratio

0.0 to .74 .75 to .99 1.0 to 1.99 > 2.0

1 to 4% None Very Low Low Moderate

5 to 9% Very Low Low Moderate High

10 to 14% Low Moderate High Extreme

15.0 to 100% Moderate High Extreme Extreme

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Inland Flooding - Logic ReviewInland Flooding - Logic Review

ERP Grid

Excessive Rainfall PotentialHigh Potential…15% or greaterModerate Potential…10 to 14%Slight Potential…5 to 9%Nominal Potential…1 to 4%

Flooding Potential (QPF/FFG)High Potential… > 2.0Moderate Potential… 1.0 to 1.99Slight Potential… 0.75 to 0.99 Nominal Potential… < 0.75

QPF/FFG Ratio

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Inland Flooding Tool - OutputInland Flooding Tool - Output

• Issues to Overcome– 6 hourly QPF and FFG

– Multi-period events (accumulated rain; changing FFG)

– Multi-day events (QPFmax ?)

– Perhaps probabilistic QPF against FFG

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The Tornado HazardThe Tornado Hazard

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Tornado - Tool InputsTornado - Tool Inputs

• The tool uses the graduated SPC tornado probabilities, along with consideration for the strongest potential tornado (tornado vs. significant tornado; that is, the SPC ‘hatched’ areas).

• The probabilities are extracted from the Day 1, Day 2, and Day 3 Probability Outlooks to determine the event composite maximum, which is returned to the forecaster as the first-guess field.

• WFO enhancements are then advocated to account for local effects such as coastal convergence, low level boundaries, enhancements to the distribution of buoyancy/shear, etc.

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(for assessing Day1)

Tornado Probability (ptor) Significant Tornado Probability (pxtor)

ThreatLevel

ptor < 2%None

ptor > 2% and < 5%Very Low

ptor > 2% and < 5% and pxtor > 10% OR ptor > 5% and < 15%

Low


Moderate


High

ptor > 45%Extreme

Tornado - Logic SummaryTornado - Logic Summary

• Part #1 - Assessing Day 1 … the Tornado SmartTool uses the logic contained in the table below to initialize the threat/impact output on GFE. The Probability of Tornado (ptor) guidance is used as the primary gridded input with threat level graduations sorted similarly to the SPC prescribed thresholds to foster message continuity. Then, to complete the Day 1 assessment, the tool checks the Probability of Significant Tornadoes (pxtor). If it is greater than or equal to 10 percent, it raises the derived level up by one.

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(for assessing Day 2)


• Part #2 – Assessing Day 2 … the Tornado SmartTool then uses the logic contained in the table below to adjust the output. It uses the Probability of Total (Combined) Severe Weather (ptotsvr) and Total Significant Severe Weather (ptotxsvr) as a proxy for tornado probability. The thought is that given the physical expanse of tropical cyclones (given the existing TC Watch or Warning in your area), the threat for combined severe weather on Day 2 is most likely tornado related.

Total Severe Wx Probability (ptorsvr)Total Extreme Severe Wx Probability (ptotxsvr)

Threat Level

ptotsvr < 5%None

ptotsvr > 5% and < 15%Very Low

ptotsvr > 5% and < 15% and ptotxsvr > 10% OR ptotsvr > 15% and < 60%

Low

ptotsvr > 15% and < 60% and ptotxsvr > 10% OR ptotsvr > 60%

Moderate

ptotsvr > 60% and ptotxsvr > 10%High

N/AExtreme

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(for assessing Day 3)


• Part #3 – Assessing Day 3 … the Tornado SmartTool then uses the logic contained in the table below to further adjust the output. Once again it uses the Probability of Total (Combined) Severe Weather (ptotsvr) and Total Significant Severe Weather (ptotxsvr) as a proxy for tornado probability. Future updates of the tool will likely allow for user selection of which combination of days (e.g., of Day 1, Day 2, and/or Day 3) to include or exclude within the event composite maximum calculation.

Total Severe Wx Probability (ptorsvr) Total Extreme Severe Wx Probability (ptotxsvr)

Threat Level

ptotsvr < 5%None

ptotsvr > 5% and < 15%Very Low

ptotsvr > 5% and < 15% and ptotxsvr > 10% OR ptotsvr > 15% and < 60%

Low

ptotsvr > 15% and < 60% and ptotxsvr > 10% OR ptotsvr > 60%

Moderate

N/AHigh

N/AExtreme

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Tornado - Impact GraphicTornado - Impact Graphic

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Once tool execution is complete, the WFO forecaster can make refinements to account for local effects. Also, they may want to factor in the forecast uncertainty of the cyclone itself (e.g., track, intensity, and size), especially if the tornado threat is not confined to Day 1. When finished, the graphic is ready to be produced and posted to the web.

Tornado Impact

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Closing CommentsClosing Comments

• 2008 initiative for the national Experimental Tropical Cyclone Hazards for select offices.

• Graphical Hazards available from many local offices in graphical HLS; eventual migration to national page.

• Acquire all necessary input data in gridded form for GFE use.

• Complete Version 1.x of all SmartTools with GSD; use test data.

• Coordinate with other Threat/Impact teams (regional and national).

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using tropical cyclone wind speed probabilities to improve public and marine text forecasts

Documents

specified forecast hour

hour forecast period

specified wind speed

wind speed forecasts

specified threshold

best forecast

probability of sustained

tropical cyclones tc